Eclipse, Java, JRuby, Cucumber and ATDD
Background

So what is it that we want to do? Quite simply. We want to be able to build a software system from the ground up based upon acceptance criteria rather than some dream or vision a particular person had after eating some strange food.

How do we do this if our language of choice is Java, we are using Eclipse, and we are running on Mac?

Prerequisites for Eclipse

1. You are running Mac OS 10.6.6
2. You have installed Eclipse Helios

Installing JRuby from source

The hard way (for us geeks):

1. Download the latest jruby from "http://jruby.org/download"

2. It should download something like: "jruby-bin-[VERSION].tar.gz", e.g. "jruby-bin-1.6.0.RC1.tar.gz"; all subsequent steps will refer to the example version

3. Create a directory: "/Library/jruby", from a command line: mkdir /Library/jruby

4. Copy the jruby source to "/Library/jruby"

5. Extract the jruby directory to "/Library/jruby", from a command line: "tar -xvf jruby-bin-1.6.0.RC1.tar.gz"

6. Add the following to your ~/.bash_profile:
	a. "export JRUBY_HOME=/Library/jruby/jruby-1.6.0.RC1"
	b. "export PATH=$PATH:$JRUBY_HOME/bin"

7. Restart your command line, or resource your ~/.bash_profile: "source ~/.bash_profile"

8. Test by running "jruby -v"

The easy way (for us efficient people that happen to be running macports):

1. Run from command line: sudo port install jruby

Setting up Cucumber and JRuby

1. Run from command line: sudo jruby -S gem install cucumber

Get going

1. Create a new workspace in Eclipse named "calculator"

2. Create a new java project called "calculator"

3. Create a directory named "features" under the root of calculator

4. Create a new file under "features" named "add_two_numbers.feature"

5. Add the following to the file

Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers
Scenario: Add two numbers
Given I have a calculator
When I add the numbers 1 and 2
Then I get 3

6. From the command prompt in your project directory, run: "jruby -S cucumber features". You should see the following output:

Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/add_two_numbers.feature:6
When I add the numbers 1 and 2 # features/add_two_numbers.feature:7
Then I get 3 # features/add_two_numbers.feature:8

1 scenario (1 undefined)
3 steps (3 undefined)
0m0.046s

7. Now, create a directory called "steps" under your "features" directory

8. In your steps directory, create a file called "calculator_steps.rb"

9. Add the following to the file:

require 'rspec'
require 'java'
$CLASSPATH << class="s2">'.') + "/bin/"
include_class Java::com.seventytimessevengroup.Calculator

Given /I have a calculator/ do
end

When /I add the numbers (\w+) and (\w+)/ do |first_number, second_number|
<
end

Then /I get (\w+)/ do |result|
end

10. From the command prompt in your project directory, run: "jruby -S cucumber features".

You should see the following output:
Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/steps/calculator_steps.rb:5
When I add the numbers 1 and 2 # features/steps/calculator_steps.rb:8
Then I get 3 # features/steps/calculator_steps.rb:11

1 scenario (1 passed)
3 steps (3 passed)
0m0.032s

11. This is great, we are all green, now, let's try to call the code we wish we had. Add this code to your steps:

require 'rspec'
require 'java'
$CLASSPATH << class="s2">'.') + "/bin/"
include_class Java::com.seventytimessevengroup.Calculator

Given /I have a caclulator/ do
	@calculator = com.seventytimessevengroup.Calculator.new
end

When /I add the numbers (\d+) and (\d+)/ do |first_number, second_number|
end

Then /I get (\w+)/ do |result|
end
12. From the command prompt in your project directory, run: "jruby -S cucumber features".

You should see the following output:
Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/steps/calculator_steps.rb:5
uninitialized constant Calculator (NameError)
./features/steps/calculator_steps.rb:6:in `/I have a calculator/'
features/add_two_numbers.feature:6:in `Given I have a calculator'
When I add the numbers 1 and 2 # features/steps/calculator_steps.rb:9
Then I get 3 # features/steps/calculator_steps.rb:12

Failing Scenarios:
cucumber features/add_two_numbers.feature:5 # Scenario: Add two numbers

1 scenario (1 failed)
3 steps (1 failed, 2 skipped)
0m0.027s

13. Maybe we should now make our class called "Calculator.java" and add the following code to it.

package com.seventytimessevengroup;

public class Calculator {
	public Calculator() {
	}
}

14. From the command prompt in your project directory, run: "jruby -S cucumber features". You should see the following output:

Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/steps/calculator_steps.rb:5
When I add he numbers 1 and 2 # features/steps/calculator_steps.rb:9
Then I get 3 # features/steps/calculator_steps.rb:12

1 scenario (1 passed)
3 steps (3 passed)
0m0.032s

15. Great, now let's continue down our scenario and add two numbers. Add the following to your "calculator_steps.rb":

require 'rspec'
require 'java'
$CLASSPATH << class="s2">'.') + "/bin/"
include_class Java::com.seventytimessevengroup.Calculator

Given /I have a caclulator/ do
	@calculator = com.seventytimessevengroup.Calculator.new
end

When /I add the numbers (\d+) and (\d+)/ do |first_number, second_number|
	@calculator.add(first_number.to_i, second_number.to_i)
end

Then /I get (\w+)/ do |result|
end

16. From the command prompt in your project directory, run: "jruby -S cucumber features".

You should see the following output:
Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/steps/calculator_steps.rb:5
When I add the numbers 1 and 2 # features/steps/calculator_steps.rb:9
undefined method `add' for # (NoMethodError)
./features/steps/calculator_steps.rb:10:in `/I add the numbers (\d+) and (\d+)/'
features/add_two_numbers.feature:7:in `When I add the numbers 1 and 2'
Then I get 3 # features/steps/calculator_steps.rb:13

Failing Scenarios:
cucumber features/add_two_numbers.feature:5 # Scenario: Add two numbers

1 scenario (1 failed)
3 steps (1 failed, 1 skipped, 1 passed)
0m0.033s

17. Now let's add our add method to our Calculator object.

package com.seventytimessevengroup;

public class Calculator {
	private int result;

	public Calculator() {
	}
	
	public void add(int firstNumber, int secondNumber) {
		result = firstNumber + secondNumber;
	}
}
18. From the command prompt in your project directory, run: "jruby -S cucumber features".

You should see the following output:
Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/steps/calculator_steps.rb:5
When I add the numbers 1 and 2 # features/steps/calculator_steps.rb:9
Then I get 3 # features/steps/calculator_steps.rb:13

1 scenario (1 passed)
3 steps (3 passed)
0m0.031s

19. Now, to complete our feature step definition:

require 'rspec'
require 'java'
$CLASSPATH << class="s2">'.') + "/bin/"
include_class Java::com.seventytimessevengroup.Calculator'

Given /I have a calculator/ do
	@calculator = com.seventytimessevengroup.Calculator.new
end

When /I add the numbers (\d+) and (\d+)/ do |first_number, second_number|
	@calculator.add(first_number.to_i, second_number.to_i)
end

Then /I get (\w+)/ do |result|
	@calculator.result().should == result.to_i
end

20. Now we need to finish our Calculator object.

package com.seventytimessevengroup;

public class Calculator {
	private int result;

	public Calculator() {
	}
	
	public void add(int firstNumber, int secondNumber) {
		result = firstNumber + secondNumber;
	}
	
	public int result() {
		return result;
	}
}

21. From the command prompt in your project directory, run: "jruby -S cucumber features". You should see the following output:
Feature: Add two numbers
In order to add not have to use my head
I want to add two numbers

Scenario: Add two numbers # features/add_two_numbers.feature:5
Given I have a calculator # features/steps/calculator_steps.rb:5
When I add the numbers 1 and 2 # features/steps/calculator_steps.rb:9
Then I get 3 # features/steps/calculator_steps.rb:13

1 scenario (1 passed)
3 steps (3 passed)
0m0.035s

22. And there you have it, a calculator fully acceptance-test driven.

23. And if you really wanna have fun, but not sure if you need it, add a junit file "CalculatorTest.java"

package com.seventytimessevengroup.tests;

import static org.junit.Assert.*;

import org.junit.Test;

import com.seventytimessevengroup.Calculator;

public class CalculatorTest {
	private final Calculator calculator = new Calculator();
	
@Test
	public void addTwoNumbers() {
		calculator.add(1, 2);
		assertEquals(3, calculator.result());
	}
}

24. How about that, fully test-driven as well, not sure why you need this last one though.